Mr Cruz's advisers had targeted Indiana as the Texas senator's best hope of halting Mr Trump's march to the nomination.

"We gave it everything we've got, but the voters chose another path," he told supporters in Indiana.

His departure means Mr Trump is now the presumptive Republican nominee, with plenty of state contests this month and next to reach the 1,237 delegates required to win.

The New York businessman is the first nominee since Dwight Eisenhower in 1952 to lack any previous experience of elected office.

Ohio Governor John Kasich has vowed to remain in the Republican race, but trails far behind Mr Trump in terms of delegates.

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Media captionTed Cruz: "With a heavy heart but with boundless optimism we are suspending our campaign"

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Media captionJust after the announcement of the end of his campaign Ted Cruz accidentally struck his wife Heidi

The Cruz party is over - Anthony Zurcher, BBC News, Indianapolis

Turn out the lights, the party's over. Ted Cruz and the #NeverTrump movement threw everything they had at Donald Trump in Indiana, and it wasn't enough. It wasn't even close to enough.

They outspent him by more than a million dollars. Mr Cruz practically took up residence in the state for the past two weeks. He named Carly Fiorina as his running mate. Nothing worked.

If there was a defining moment of the Indiana campaign, it was Mr Cruz's fruitless attempt to reason with a group of pro-Trump supporters on Sunday.

Every argument he advanced was rebuffed. Every bit of evidence of Trump malfeasance was denied. Mr Cruz was shouting in the wind.

In the coming days there will be a great reckoning, as the party comes to terms with the prospect of Mr Trump as their standard bearer in the autumn. Some will make peace. Some will despair. Others will say "I'm with her" and reluctantly move to Hillary Clinton's side.

Ted Cruz did not offer any congratulations or support to Mr Trump, and did not even mention his name, Politico says, although he offered what it described as a veiled jab, saying that America was kind, "not boastful or mean-spirited"

Mr Trump is well behind Hillary Clinton in national polls and is struggling to reunite voters who supported Republican presidential candidate Mitt Romney in the 2012 election, says the New York Times

The Huffington Post says that Bernie Sanders will benefit from Mr Cruz's departure, as Mr Trump concentrates his fire on Mrs Clinton, who is forced to fight on two fronts, and news coverage focuses more on the Democratic race

It is now increasingly likely that Mr Trump will face Mrs Clinton in the autumn in the battle to succeed President Barack Obama, who will be leaving the White House after two terms.

But Republicans have expressed reservations about Mr Trump's outspoken remarks, which have offended women and Hispanics.

There are also concerns about some of his policies on immigration and national security, like building a wall on the southern US border paid for by Mexico, a ban on Muslims coming to the US and the killing of the families of terrorists.